Tensioning rails are preferably used for traction mechanism drives of internal combustion engines, such as gasoline engines or diesel engines of motor vehicles. However, they may also be used in watercraft or aircraft. The continuously revolving traction mechanism used is often designed as a chain or belt. When a chain is used, it is preferably made up of steel links.
The traction mechanism is situated between different shafts, for example between a crankshaft, one or multiple intermediate shafts, and/or one or multiple camshafts, for the force transmission. Thus, for example, force transmission may take place from a drive wheel, such as that of a crankshaft, to a driving wheel, such as that of a camshaft.
Due to the frequently fluctuating load on the traction mechanism, it is advantageous to tension the traction mechanism. For this purpose, the tensioning rail is pressed against the continuously revolving traction mechanism until the traction mechanism reaches the desired pretension. The tensioning rail generally presses on the slack span of the traction mechanism, so that the traction mechanism slides across the tensioning rail. It has proven to be advantageous if the tensioning rail is arched in the longitudinal direction. Thus, it is not possible for the traction mechanism to jam in the tensioning rail.
The tensioning rail includes a base wall and two cheeks which protrude from the base wall. The base wall at its front side may come into contact with the traction mechanism in order to tension it. The base wall facing the front side, i.e., transversely with respect to the longitudinal direction of the guide rail, often is likewise arched. In addition, on the front side the base wall may include a slide lining which comes into contact with the traction mechanism. The cheeks generally protrude from the rear side of the base wall. The cheeks are preferably situated in parallel to one another and/or symmetrically with respect to the tensioning rail. The cheeks are used for increasing the stability of the tensioning rail. In addition, the cheeks provide an advantageous option for transmitting forces for tensioning the traction mechanism to the tensioning rail.
Furthermore, it is provided that the tensioning rail includes at least one U-shaped profile section and one T-shaped profile section, each of which is formed by the base wall and the cheeks. A tensioning rail including profile sections of this type is known from Published Unexamined Patent Application US 2012/0015769 A1 . A U-shaped profile section is situated between two T-shaped profile sections, viewed in the longitudinal direction. The two T-shaped profile sections each include a cross-hole for a pivot bearing. Due to the shape transition from the U-shaped profile to the particular T-shaped profile, the T-shaped profile sections are particularly advantageously suited for introducing tension forces into the tensioning rail. In practice, however, it has been found that, due to the small width of the guide rail in the particular T-shaped profile section and the cross-hole formed there for the pivot bearing, there is a risk that during operation the guide rail may tilt slightly about a longitudinal axis. To preferably prevent this, the guide rail must be manufactured very precisely. The level of effort for manufacturing such a guide rail is therefore very high.